Seal for resisting high pressures



Feb. 22, 1949. D. J. WHlTTlNGHAM 6 SEAL FOR RESISTING HIGH PRESSURES Filed Jan. 2, 1946 Pie. 1 i

FiG.6 119 David J. Whittingham ,emw. wwa

Patented Feb. 22, 1949 SEAL FOR RESISTING HIGH PRESSURES David J. Whittingham, Watertown, N. Y., assignor to The New York Air Brake Company, a corporation of New Jersey Application January 2, 1946, Serial No. 638,626

This invention relates to packing for pistons, piston-rods and the like, and has to do with socalled O-rings" or grommets of rubber, synthetic rubber substitutes, or other resilient compositions. I

These highly resilient rings, when used to seal against high pressures, are likely to extrude into the clearance between the packed surfaces. Efl'orts to cure the difficulty by the use of hard plastic or metal snap rings on one or both sides of the toric resilient ring have been made without success. Applicant after extensive test work has determined that a major cause of failure in the prior devices was occurrence of extrusion at the joint or gap in the snap ring.

The use of an improved joint at the gap of an expansible (or contr'actible) ring is an important feature of the invention. That the construction is successful is demonstrated, for pressures as high as 5000 p. s. i. have been withstood under the conditions of practical service.

The invention may be variously applied. The rings may be assembled in a groove in the encircled part, or in a groove in the encircling part.

In the first case there is a general resemblance to "piston rings whereas the second case generally resembles constructions used with rod packings or plunger packings. If the pressure diiferential against which the seal acts is undirectional only one extrusion-resisting ring is needed. It must be placed on the low pressure side. If the pressure differential reverses. two rings are needed, one at each side of the resilient ring.

Preferred embodiments of the invention will now be describedby reference to the accompanying drawing, in which:

Fig. 1 is an edge view of the ring showing the gap.

Fig. 2 is a view of the beveled face of the ring showing the gap. 6 I Fig. 3 is an enlargedview of the gap as viewed in Fig. 1,

Fig. 4 is an axial section through two packed cylindrical parts, showing the improved packing arranged to seal against a unidirectional pressure diflerential.

Fig. 5 is an elevation of the grooved part shown in Fig. 4 with the rings assembled therewith.

Fig. 6 is a view similar to Fig. 4 showing the improved packing arranged to seal against a pressure differential which reverses.

Much discussion has centered about the idea of allowing a resilient toric ring sufllcient clearance to roll slightly in an axial direction so as to be kneadedf The drawings show clearance,

2 Claims. (Cl. 309-23) to permit rolling in an axial direction, simply to the contrary it is shown compressed merely in] indicate that the invention may be used where such clearance is present. At high pressures, clearance to permit rolling-is immaterial provided the volume of the ring is less than the volume of the groove. Deformation caused by pressure will distort the ring so much more severely that the deformation by rolling ceases to be significant, assuming that it ever was.

Refer first to Figs 1-5. In Fig. 4, 11 indicates an encircled member such as a cylindrical piston,

rubber-like resilient material dimensioned to form the primary seal. As shown in Fig. 4it is not deformed as it is when subject to the differential pressure against which it is intended to'seal. On

directions radial to the piston. So compressed the illustrated toric ring does not quite span the interval between side It and the proximate plane face I! of ring l8. It is considered immaterial whether it does or not. Ring l8 has one conical face N! which mates with conical side I5 of the groove.

Ring I8 is split and elastic, and preferably of material. As used in a piston it may have a slight expansiv tendency but this is not considered indis ensable. It is desirable that the ring inherently tends to seat on the wall of cylinder l2 around the entire periphery and a one piece ring is the logical choice.

The ring l8 has a step joint, best shown in Fig. 3. A tongue 2| enters rebate 22 formed on the side of ring l8 remote from ring l6 (1. e.

the conical or beveled side). Tongue 2| merges into the adjacent portion of the ring by means of .an inclined surface 23 and the opposite overlapping portion 24 is beveled to a feather edge. Thus a shallow recess indicated at 25 in Fig. 5 is present and receives a displaced portion of ring l6 when the pressure differential acts.

Stating direction with reference to Fig. 4, the pressure differential urges ring IE to the right forcing it againstthe flat side. of ring l8. Thus ring f8 is forced up the conical surface l5, and caused to seatoutward on cylinder l2, so that there 'is no interval through which any portion of ring 16 can extrude. either around the ring or through the joint therein. The tapers at 23 and 2B" facilitate contracting motions of ring l8. yStill referring to Fig. 4, it is obvious that H could be the encircling member and I2 the encircled member. Thisimplies a reversed curvature of ring l8. Functionally the only material difference would be that the wedging action would eaue the ring Hi to contract. n To afio'rd an amrmative illustration of this possibility, Fig. 6 has been included. In addition,

and as an independent optional feature, two rings similar to ring [8 are shown, with a ring similar to 16 between them. This ailords a seal against pressure differentials acting in either direction.

In Fig. 6 similar parts are given the same numbers as in Figs. 1-5 increased by 100.

The encircled member is l I I and the encircling member H2. The groove is formed in the latter V and has a cylindrical bottom H3 and two conical sides 5. The resilient toric ring H6 is placed between two rings H8 each with a. step joint such asth'atshown in Fig. 3 and a beveled face H9 coacting with a corresponding side H5 of the roove. v I I The rings shown in Figs. 4 and'6 are shown slightly'deformed. When 'unstressed they are circular in cross-section. Other cross-sections, ovoid or-elliptical, are possible but ofier no ap parent advantage. Since grommets of such cross-section have been proposed and used their illustration'is deemed unnecessary.

The precise form of the toric ring, and the clearance'aiforded it are subject to variation. I The invention is concerned with the exparisible extrusion resistingring (or rings) l8. The use of aneizptmsible ring with a step joint and some means to cause thering to expand as the toric ring isdisplaced by pressure, and before extrusion starts, is'the vital thing. The beveled ends of the recess 25 (Fig. 5) minimize local severe deformation of ring l6 and favor expansion or contraction of the ring l 8-without interference by or damage to ring l6. Modifications consonantfwith the attainment of these objectives are obviously possible and within the scope of the invention. In the claims the terms piston and cylinder elements will be used in their broadest. and most generic sense to cover two relatively face adapted t mate v,with the conical side portion of the groove in said one component, a cylin- ,,dric'al face adapted to mate with the cylindrical face of said other component, and a third face .adapted tob'e presented toward said rubber-like ring, said guard ring being of hard elastic material and split so that it may expand and contract as it moves in contact with the conical side portion of the groove, the split beingof stepped 'configuration and comprising a slender tongue which projects from the portion of .the ring at one'side of, the split, overlapsthe-sjplit and'seats-on a mating surface in a recess formed in the, ring" at the other side of the split, said mating suriace being substantially parallel "with andsaid recess being formed 'in said third face of the guard ringjthe tongue 'andthe recess-with which it meets having inclined ends-whereby the tendency to-pinch the rubber-filtering is minimized.

2. A guard ring according to claim 1 in which the ring has an elastic reaction, tending'to seat its cylindrical face against thecylindrical face of said other component, whenthe ring is assembled with said cylinder-piston assembly.

'DAVID J.'W HITTING,HAM. REFERENCES CITED The following references are of record in the file of this patent;

v UNITED STATES PATENTS Number Name Date 870,428 Graham Nov. 5, 1907 2,276,027 Dick Mar." 10, 1942 Smith May 6, 1947 February 22, 1949.

5 Certificate of Correction Patent No. "2,462,586. a

DAVID J. WHITTINGHAM It is hereby certified that error appears in the printed specification of the above numbered patent requiringcorrection as follows:

Column 4, line 12, claim 1, after the word "conical strike out face;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office Signed and sealed this 21st day of June, A. D. 1949. l 

